In order to investigate the effect of C and Cu elements on the microstructure and properties of Al0.3CoFeNi high-entropy alloys,vacuum arc melting was used to prepare four kinds of high-entropy alloys:Al0.3CoFeNi,Al0.3CoFeNiC0.1,(Al0.3CoFeNi)99.9Cu0.1 and(Al0.3CoFeNiC0.1)99.9Cu0.1.Their crystal structures and microstructures were analyzed by an X-ray diffractometer,scanning electron microscope and transmission electron microscope,respectively.The test results are as follows.Al0.3CoFeNi high-entropy alloy had a single FCC structure and the additions of 1% C and 0.1% Cu respectively did not change its crystal structure,but nano-particle L12 phase precipitated in the alloy.And the addition of 0.1% Cu reduced the size of L12 phase.The particle size of the L12 phase was about 30 nm when 1% C alone was added,and the particle size of the L12 phase was reduced to 10 nm with another 0.1% Cu added.The mechanical property test results show that(Al0.3CoFeNiC0.1)99.9Cu0.1 alloy had the best comprehensive performance,and its compressive yield strength,compressive strength,compression ratio and micro hardness score could reach 974 MPa,2532 MPa,51.9% and 511.7 HV.